Friday, June 18, 2010

MRSA and survival

Dr. Dan Diekema recently blogged about a new study published in JAMA that shows that respiratory tract MRSA carriage/infection is linked to high mortality in cystic fibrosis patients. He raises an interesting question about why MRSA, and not MSSA, is associated with worse outcome among cystic fibrosis patients especially since there is no evidence to show that MRSA is intrinsically more virulent than MSSA (Now, this is debatable as there are studies that show that MRSA is more virulent than MSSA, however the justifications behind why this is the case are controversial).

Nevertheless, Dr. Diekema’s question reminded me of an article I read on toxoplasma in last week’s Economist. Toxoplasma is a pathogen that’s a close cousin to Plasmodium, the bug that causes malaria. However, despite its high prevalence, symptoms among people infected with toxoplasma are mild and the bug doesn’t seem to cause a lot of damage, UNTIL scientists discovered that rats infected by toxoplasma exhibit more risky behavior, which suggests that the bug is interfering with the brain.

A separate study on toxoplasma in humans found that people involved in road accidents were almost three times more likely to be infected by toxoplasma than those who had not been. Some are going as far as saying that toxoplasma is altering the culture of entire societies.

So, here is my theory to answer Dr. Diekema’s question, maybe MRSA is affecting patients’ psychology and/or behavior in a way similar to that of toxoplasma? Or could it be that MRSA colonization/infection leads to higher susceptibility to toxoplasma infection, which leads to more risky behavior? i.e. not following hand hygiene compliance. I wonder what kind of study we can do to prove my theory.


  1. Stuff You Should Know has a great podcast on toxoplasma:

    How has toxoplasma turned the world into zombies?
    Tuesday, July 14, 2009 10:34 AM
    Toxoplasmosis is a parasitic infection that favors cats, but it can also be found in humans. Discover the disturbing details of how toxoplasma gondii finds a host -- and how it affects human beings -- in this podcast from

  2. Countries with higher rates of toxoplasma also are more likely to win the World Cup